Abstract

The vortex propagation exhibits rectificationeffect in Nb superconductors with spacing-graded density of holes. A rectified dc voltage is obtained when the vortex lattice is driven by accurrent. The asymmetric geometry of the pinning array produces a significant influence on the vortex motion. The rectified voltage depends considerably on the amplitude of the applied accurrent and the magnetic field. The experimental results reveal a drastic change of the vortexrectification for magnetic field above∕below the first matching field. The reason may be that the interstitial vortices are formed in the film above the first matching field. A reversible vortex motion is induced by the interstitial vortices for the field above the first matching field.

This work was supported by the National Science Council of the Republic of China under Grant Nos. NSC 94-2112-M-018-004 and NSC 95-2112-M-009-029. It is also in part supported by MOEAU program of Nation Chiao Tung University.